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1.
The subject of the study was the taxonomy of the ammonite fauna from the Upper Barremian marls and marly limestones of the Donji Milanovac Formation outcropped at the Boljetin Hill (Danubicum Unit). These sediments yielded a rich ammonite fauna which included also representatives of two superfamilies, Desmoceratoidea and Silesitoidea. The Desmoceratoidea include the family Barremitidae to which belong Plesiospitidiscus boljetinensis n. sp., Barremites balkanicus, Montanesiceras breskovskii n. sp., Barremitites strettostoma strettostoma and B. panae, Torcapella serbiensis n. sp., Pseudohaploceras tachthaliae, P. portaeferreae, Melchiorites haugi and Patruliusiceras cf. crenelatum. The Silesitoidea are represented by the family Silesitidae with Silesites trajani and S. seranonis. With the exception of the new, possibly endemic species, Plesiospitidiscus boljetinensis n. sp., Montanesiceras breskovskii n. sp., and Torcapella serbiensis n. sp., these taxa are common in the Tethyan regions. The studied deposits with ammonites belong to the lower part of the Late Barremian, in particular to the upper part of the Toxancyloceras vandenheckii ammonite Zone up to the lower part of the Imerites giraudi Zone.  相似文献   

2.
An early Berriasian (Berriasella jacobi Zone) ammonite fauna is described for the first time from the Alborz Mountains in northwest Iran. It has been collected from a section located near the village of Shal (Talesh region); in addition to rare phylloceratids, lytoceratids and Neolissoceras, the majority of ammonites belong to the neocomitid subfamily Berriasellinae. With the exception of a new genus and species, Taleshites fuersichi, these taxa are common in European and North African Tethyan successions. Associated calpionellids confirm the early Berriasian age of the ammonite-bearing levels.  相似文献   

3.
Sediments of Early Aptian age in Bulgaria can be assigned to four different facies: platform carbonates (Urgonian complex), shallow-water siliciclastics, hemipelagic and flyschoid siliciclastics. The taxonomic analysis of the ammonite faunas of 18 sections from these four different facies resulted in a revision of the existing ammonite zonation scheme so far applied in Bulgaria and adjoining areas. A new biostratigraphic scheme, which bridges the western and eastern Tethys, is thereby proposed for the Lower Aptian of Bulgaria.The Upper Barremian Martelites sarasini Zone is characterized in its upper part by the Pseudocrioceras waagenoides Subzone in the shallow-water sections and by a horizon with Turkmeniceras turkmenicum in the deep-water settings. The Upper Barremian/Lower Aptian boundary is fixed by the first appearance of Paradeshayesites oglanlensis. For the Lower Aptian the following ammonite zones were established (from bottom to top): The Paradeshayesites oglanlensis Zone, the Deshayesites forbesi Zone (= formerly Paradeshayesites weissi Zone) including the Roloboceras hambrovi Subzone in the upper part, the Deshayesites deshayesi Zone including the Paradeshayesites grandis Subzone in the upper part and the Dufrenoyia furcata Zone. The Lower–Middle Aptian boundary has been defined by the appearance of species belonging to the genera Epicheloniceras and Colombiceras.The Lower Aptian ammonite faunas of Bulgaria, allow an interregional correlation with other areas of the Tethyan Realm. The presence of Turkmeniceras in the Upper Barremian enables a correlation with the Transcaspian region, whereas Roloboceras, Koeneniceras and Volgoceratoides found in the middle part of the Lower Aptian are more typical representatives of the ammonite faunas in northern Europe (England, Germany, Volga region).The analysis of the ammonite successions in combination with sedimentological observations enable us to conclude that the marls and marly limestones of the Lower Aptian studied here also cover the interval of the Oceanic Anoxic Event 1a. An interval of thin-laminated clays, rich in organic matter, was identified in the upper part of the D. forbesi Zone (Roloboceras hambrovi Subzone). This interval is characterized by a total lack of benthic faunas.  相似文献   

4.
《Cretaceous Research》2008,29(1):9-26
An analysis of the stratigraphic distribution of ammonite faunas collected from several sections in the Essaouira-Agadir area (western High Atlas, Morocco) has enabled the establishment of a detailed succession of assemblages for the uppermost Hauterivian to lower Upper Barremian interval. All Mediterranean standard zones of this interval have been identified. The correlation potential of bioevents which define and characterise these units is discussed. Two significant regional hiatuses, one at the Hauterivian/Barremian boundary, the other involving the lower part of the Kotetishvilia nicklesi Zone, are related to third-order sea level falls. Moreover, the upper part of the succession corresponding to the upper Toxancyloceras vandenheckii Zone and the entire Heinzia sartousiana Zone is markedly condensed. The taxonomic composition of the ammonite assemblage reveals a strong Mediterranean character, yet, it shows some peculiar features as well.  相似文献   

5.
The most complete Hungarian Valanginian perisphinctid ammonite fauna of the Mecsek Mountains (South Hungary) consists of 14 species is reported. Thurmanniceras sp. aff. otopeta, Fuhriella michaelis, F. cf. hoheneggeri, Sarasinella cf. ambigua, Neocomites (Neocomites) subtenuis, Neocomites (Eristavites) platycostatus are reported for the first time from Hungary. The fauna comprises 23 ammonite species and is reported from Valanginian tuffaceous marl, alternating marl–limestone beds and loose limestone blocks. Two studied sections represent the Lower Valanginian Thurmanniceras pertransiens and partly the Busnardoites campylotoxus Zones while ammonites from loose blocks indicate the latter and possibly the Upper Valanginian Saynoceras verrucosum Zone. Variations in the faunal composition of the marl beds and the limestone blocks respectively, refer to the contrast between the ammonite ecological demands. Phylloceratid and lytoceratid ammonites prevail the marl beds, while olcostephanid and neocomitid ammonites prevail the shallower platform-like limestones. Sediment accumulation rate in that palaeo volcano related environment was high and bottom currents frequently washed together ammonite shells or filled their body chambers with smaller ammonite shell fragments. Due to the fast sedimentation the sections represent only partially the recognized ammonite zones therefore long-term or even infra-regional correlation was not possible. Palaeobiogeographically, the ammonite fauna has Mediterranean character and it shows close relationships to the Valanginian faunas of the Bakony Mts. (Hungary), Western Carpathians (Slovakia), Northern Calcareous Alps (Austria), and SE Spain. The presence of Fuhriella species is remarkable and enlarges our knowledge on the distribution of this enigmatic ammonite taxon adding new data to its Valanginian stratigraphic position and geographic distribution.  相似文献   

6.
A small brachiopod fauna is described from the upper part of the Yenduyet Formation near Son La, northwest Vietnam. The fauna includes the following species: Peltichia kwangtungensis (Zhan), Acosarina minuta (Abich), Rhipidomella hessensis King, Schuchertella cf. cooperi Grant, Derbyia sp., Waagenites soochowensis (Chao), Spinomarginifera chenyaoyanensis Huang, and a Marginiferinae gen. and sp. indet. The fauna is most closely correlated with brachiopods from the lower Changhsingian Stage of South China and the lyttoniid fauna from the Huai Tak Formation of northwest Thailand. In view of these correlations, an early Changhsingian (Late Permian) age is proposed for the Son La brachiopod assemblage.  相似文献   

7.
The Dvuyakornaya Formation section in the eastern Crimea is described and subdivided into biostratigraphic units based on ammonites, foraminifers, and ostracodes. The lower part of the formation contains first discovered ammonites of the upper Kimmeridgian (Lingulaticears cf. procurvum (Ziegler), Pseudowaagenia gemmellariana Olóriz, Euvirgalithacoceras cf. tantalus (Herbich), Subplanites sp.) and Tithonian (?(Lingulaticeras efimovi (Rogov), Phylloceras consaguineum Gemmellaro, Oloriziceras cf. schneidi Tavera, and Paraulacosphinctes cf. transitorius (Oppel)). Based on the assemblage of characteristic ammonite species, the upper part of the formation is attributed to the Berriasian Jacobi Zone. Five biostratigraphic units (zones and beds with fauna) distinguished based on foraminifers are the Epistomina ventriosa-Melathrokerion eospirialis Beds and Anchispirocyclina lusitanica-Melathrokerion spirialis Zone in the upper Kimmeridgian-Tithonian, the Protopeneroplis ultragranulatus-Siphoninella antiqua, Frondicularia cuspidiata-Saracenaria inflanta zones, and Textularia crimica Beds in the Berriasian. The Cyrherelloidea tortuosa-Palaeocytheridea grossi Beds of the Upper Jurassic and Raymoorea peculiaris-Eucytherura ardescae-Protocythere revili Beds of the Berriasian are defined based on ostracodes. A new biostratigraphic scale is proposed for the upper Kimmeridgian-Berriasian of the eastern Crimea. The Dvyyakornaya Formation sediments are considered as deepwater facies accumulated on the continental slope.  相似文献   

8.
The Lower Cretaceous ammonite fauna of Japan was influenced by the Tethyan, Boreal and North Pacific realms with their oceanic current patterns and ammonite distributions. The hypothesis of oceanic circulation can be utilized to interpret the existence of the “Bering Strait” and the changing position of the “Boreal front,” that is the contact region of warm and cold-water masses. To understand such a system fully, a comprehensive understanding of the geographical distribution of ammonite faunas is required. The occurrence of twenty-five ammonite species, belonging to twenty genera, is confirmed in the Barremian to Albian of Japan. Of these, 24 species are described in this paper, including Barremites macroumbilicus sp. nov. The fauna can be divided into three associations, lower, middle, and upper, indicating late Barremian, late Aptian, and late Albian of the European standard zonation. The faunal characters suggest that the habitats of these ammonite faunas may have changed during later Early Cretaceous, with faunas characterizing three different environments, i.e., nearshore, intermediate, and distal shelf to upper slope setting. Ammonites of the lower association (late Barremian) are related to those of the Tethys, Boreal European, and circum-Pacific regions, and suggest that the Early Cretaceous Katsuuragawa Basin was deposited under the influence of currents from both high latitude and equatorial areas. The occurrence of Crioceratites (Paracrioceras) suggests that the Boreal European elements, including Simbirskites and Crioceratites (Paracrioceras), transited between Northwest Europe and Japan through the Arctic Sea, indicating that the Pacific Ocean was connected with the Arctic Sea at that time. The second association (late Aptian) is composed of ammonites of the Tethyan and circum-Pacific regions. As European Boreal ammonite taxa are absent in this association, it is concluded that the Pacific Ocean probably was not connected with the Arctic Sea at the time. Consequently, the “Boreal Front,” marking the contact between warm and cold water masses, was located at mid-latitude in the “Bering Strait” region during Barremian and subsequently moved northward during Albian. The uppermost ammonite association (late Albian) also consists of Tethyan and circum-Pacific taxa. Desmoceras (Pseudouhligella) poronaicum expanded its range with northward and eastward circulation of oceanic currents, suggesting the current must have represented a warm water-mass from the equator. The species subsequently migrated from the southern Katsuuragawa Basin to the Hokkaido area during late to latest Albian.  相似文献   

9.
Palynological investigation of the Cretaceous Abu Roash, Bahariya, Kharita, Alamein, Alam El Bueib and Betty formations, encountered in the Gebel Rissu-1 well, north Western Desert, Egypt yielded 27 species of pteridophytic spores, 24 of gymnosperm pollen, 25 of angiosperm pollen and 11 of dinoflagellate cysts in addition to some acritarchs, foraminiferal test linings and freshwater algae. This enabled us to recognize five miospore biozones arranged from youngest to oldest as: Classopollis brasiliensis–Afropollis cf. kahramanensis–Dichastopollenites ghazalataensis Assemblage Zone (Late Cenomanian); Elaterosporites klaszii–Sofrepites legouxae–Afropollis jardinus Assemblage Zone (Middle/Late Albian–Early Cenomanian); Pennipollis peroreticulatus–Duplexisporites generalis-Tricolpates Assemblage Zone (Early Aptian–Early Albian); Tucanopollis crisopolensis–Afropollis sp. Assemblage Zone (Barremian) and Appendicisporites cf. tricornitatus–Ephedripites spp. Assemblage Zone (Late Neocomian).The Early Cretaceous Kharita, Alam El Bueib and the Betty formations encountered in the Gebel Rissu-1 well are interpreted to indicate oxic proximal and distal shelf deposits, characterized by type III/IV, V kerogen, which is gas prone but having little potential to produce hydrocarbons. The Upper Cretaceous Abu Roash and Bahariya formations are characterized by a distal suboxic–anoxic and marginal dysoxic–anoxic environment, and their kerogen type III/II indicates gas/oil prone nature. The Bahariya and Kharita Albian–Cenomanian sediments in the present study witnessed the onset of a semi-arid to arid climate, with local or seasonal humid conditions, based on the continuous high abundance of the elaterates pollen and Afropollis-producing plants that inhabited the paleotropical humid coastal plains.  相似文献   

10.
Northern Ireland's Jurassic succession has received relatively little detailed investigation. Late Sinemurian and early Pliensbachian strata are present in parts of north Antrim but they are poorly exposed at outcrop and have been penetrated by just a single borehole, at Portmore, in which parts of the succession are missing. Collecting from White Park Bay over more than two decades, augmented by examination of museum material, has established the presence within the Rathlin (North Antrim) Basin of ammonite zones and subzones additional to those proven in the Portmore Borehole. This suggests that parts of the Sinemurian and Pliensbachian stages, from the Obtusum Zone through to the Davoei Zone, and possibly even higher, may be preserved in onshore or nearshore parts of the basin. Despite the generally poor exposure, the material recovered encompasses more than 40 ammonite species, including several taxa that are poorly represented elsewhere in the UK, of which two, Vicininodiceras dalriatense sp. nov. and Cheltonia howarthi sp. nov., are previously undescribed.  相似文献   

11.
The Dalichai Formation with an age of Late Bajocian-Late Callovian was sampled in Central Alborz Mountains of northern Iran and studied for palynological, palaeobiogeographical and palynocorrelation purposes. Palynological studies revealed diverse and well-preserved dinoflagellate cyst assemblages and lead to identification of three zones i.e., Cribroperidiniumcrispum (Late Bajocian), Dichadogonyaulaxsellwoodii (Bathonian to Early Callovian) and Ctenidodiniumcontinuum (Early to Middle Callovian) Zones. Subzone a of the D. sellwoodii Zone (Early to Middle Bathonian) was also differentiated. This biozonation corresponds to those recognised in Northwest Europe. Furthermore, the ammonoid families recorded including Phylloceratidae, Oppeliidae, Reineckeiidae, Perisphinctidae, Haploceratidae, Parkinsoniidae and Sphaeroceratidae, which confirm the Late Bajocian to Late Callovian age, are quite similar to those of Northwest Europe and the northwestern Tethys. The close similarities of the dinoflagellate cyst assemblages and ammonite fauna of northern Iran with those of Northwest Europe and the northwestern Tethys during the Middle Jurassic indicate direct but episodic marine connection and faunal exchange between the two areas.  相似文献   

12.
A new middle Miocene vertebrate fauna from Peruvian Amazonia is described. It yields the marsupials Sipalocyon sp. (Hathliacynidae) and Marmosa (Micoureus) cf. laventica (Didelphidae), as well as an unidentified glyptodontine xenarthran and the rodents Guiomys sp. (Caviidae), “Scleromys” sp., cf. quadrangulatus-schurmanni-colombianus (Dinomyidae), an unidentified acaremyid, and cf. Microsteiromys sp. (Erethizontidae). Apatite Fission Track provides a detrital age (17.1 ± 2.4 Ma) for the locality, slightly older than its inferred biochronological age (Colloncuran-early Laventan South American Land Mammal Ages: ∼15.6–13.0 Ma). Put together, both the mammalian assemblage and lithology of the fossil-bearing level point to a mixture of tropical rainforest environment and more open habitats under a monsoonal-like tropical climate. The fully fluvial origin of the concerned sedimentary sequence suggests that the Amazonian Madre de Dios Subandean Zone was not part of the Pebas mega-wetland System by middle Miocene times. This new assemblage seems to reveal a previously undocumented “spatiotemporal transition” between the late early Miocene assemblages from high latitudes (Patagonia and Southern Chile) and the late middle Miocene faunas of low latitudes (Colombia, Perú, Venezuela, and ?Brazil).  相似文献   

13.
藏北申扎地区永珠组中上部发现了Neognathodus牙形石动物群,自下而上划分为Neognathodus cf.symmetricus-N.cf.asymmetricus组合、Neognathodus medadultimus-N.medexultimus-N.roundyi组合、Rhachistognathus sp.A-Neognathodus ultimussp.nov.组合。上述牙形石动物群指示永珠组中上部的时代为晚石炭世巴什基尔阶中期—莫斯科阶晚期。该牙形石动物群与俄罗斯地台区、北美地区和华南地区比较,显示出低分异度和低丰度的特点,表明该地区当时的生态环境并不十分利于牙形石生长,可能是当时该地区处于南半球中高纬度附近、水体温度偏冷所致。  相似文献   

14.
A selachian fauna is described for the first time from the Late Cretaceous (Campanian–Maastrichtian) of Senegal. So far, the Campanian Paki Formation has only yielded a single tooth of Rhombodus sp. whereas the Cap de Naze Formation has yielded a more diverse fauna including juvenile Cretalamna cf. Cretalamna biauriculata, Serratolamna serrata, Carcharias cf. Carcharias heathi, ?Carcharias sp., Squalicorax pristodontus, Schizorhiza stromeri, Parapaleobates sp., Rhombodus binkhorsti and Rhombodus andriesi. Teeth of juvenile Cretalamna largely dominate the assemblage. Such an assemblage confirms a Late Maastrichtian age for the unit 3 in the Cap de Naze Formation. The assemblage, although composed of cosmopolitan taxa, is similar to the contemporaneous selachian assemblage from the phosphates of Morocco.  相似文献   

15.
The 5th meeting of the IUGS Lower Cretaceous Ammonite Working Group (the Kilian Group) held in Ankara, Turkey, 31st August 2013, discussed the Mediterranean ammonite zonation, and its calibration with different ammonite zonal schemes of the Boreal, Austral and Central Atlantic realms. Concerning the standard zonation, that corresponds to the zonal scheme of the West Mediterranean province, some changes have been made on two stages. For the Valanginian, the Busnardoites campylotoxus Zone was abandoned; the upper part of the lower Valanginian is now characterised by the Neocomites neocomiensiformis and Karakaschiceras inostranzewi zones. For the upper Barremian, the former Imerites giraudi Zone is here subdivided into two zones, a lower I. giraudi Zone and an upper Martellites sarasini Zone. The I. giraudi Zone is now subdivided into the I. giraudi and Heteroceras emerici subzones, previously considered as horizons. The current M. sarasini and Pseudocrioceras waagenoides subzones correspond to the lower and upper parts of the M. sarasini Zone, respectively. The Anglesites puzosianum Horizon is kept. The Berriasian, Hauterivian, Aptian and Albian zonal schemes have been discussed but no change was made. The upper Hauterivian zonal scheme of the Georgian (Caucasus) region (East Mediterranean province) has been compared with the standard zonation. Discussions and some attempts at correlations are presented here between the standard zonation and the zonal schemes of different palaeobiogeographical provinces: the North-West European area for the Valanginian and Hauterivian, the Argentinean region for the Berriasian, Valanginian and Hauterivian, and the Mexican area for the Valanginian–Hauterivian and Aptian–lower Albian. The report concludes with some proposals for future work.  相似文献   

16.
H.G. Owen   《Cretaceous Research》2007,28(6):921-938
The ammonite biostratigraphy of the 279.35 m of sediments of mid-Late Albian–Early Albian age traversed by the Kirchrode II (1/94) boring is described. The borehole was drilled in the Hermann-Löns Park, Kirchrode (Hannover), northwest Germany, in the central region of the Lower Saxony sedimentary basin. The core commenced within the Kirchrode Mergel Member of the Gault Formation in sediments of Callihoplites auritus Subzone age and showed a Late Albian ammonite zonal succession similar to that previously described by Wiedmann and Owen from the lower part of the nearby Kirchrode I (1/91) core, with which it is correlated. The thick underlying clay sediments of the Minimus Ton Member (Middle Albian–late Early Albian) provided a relatively sparse ammonite fauna. In the Middle Albian part of the sediment succession, several hiatuses are present and only sediments of the lower Euhoplites loricatus Zone (Anahoplites intermedius Subzone) and the Hoplites dentatus Zone (Hoplites spathi Subzone) have been identified. This is followed downward by a thick sedimentary succession through the upper part of the Early Albian Douvilleiceras mammillatum Superzone (Otohoplites auritiformis Zone). Earlier mammillatum and perhaps latest Leymeriella tardefurcata Zone portions of the core straddling the Minimus Ton/Schwicheldt Ton boundary, did not yield ammonites. The underlying sediments at the top of the Schwicheldt Ton Member, consist of dark clays and mudstones with a good representation of the Leymeriella (Neoleymeriella) regularis Subzone and the uppermost part of the Leymeriella acuticostata Subzone (Leymeriella tardefurcata Zone). Of particular importance is the succession through the sediments of the L. (N.) regularis Subzone, hitherto poorly known in north Germany. A brief comparison and correlation is made with other surface and borehole sections in northern Germany and elsewhere. The Boreal and more cosmopolitan Tethyan elements of the fauna are indicated and discussed. An appendix of ammonites obtained from the Mittellandkanal section at Misburg of latest Albian, Arraphoceras (Praeschloenbachia) briacensis Subzone age, completes the study.  相似文献   

17.
Upper Hauterivian deposits in the Kurilovo area, Kamenica 1 section, NE of Niš, are described based of abundant and diverse orbitolinids. So far, the interval was assigned to the Barremian–Aptian on the geological map. Such a new age assignment results from the first detailed study carried out on the orbitolinid fauna contained in the Lower Cretaceous (upper Hauterivian) shallow-water limestones of eastern Serbia. The upper Hauterivian is documented on the basis of two key stratigraphic markers, specifically Valserina primitiva and Paleodictyoconus beckerae.In addition to these late Hauterivian index fossils, the studied section bears orbitolinids having a larger stratigraphic distribution: Cribellopsis neoelongata, Cribellopsis thieuloyi?, Montseciella glanensis, Orbitolinopsis debelmasi, Orbitolinopsis cf. debelmasi, Orbitolinopsis sp., Paleodictyoconus cuvillieri, Paleodictyoconus cf. cuvillieri, Paleodictyoconus cf. beckerae, Paleodictyoconus cf. actinostoma, Paleodictyoconus sp., Paracoskinolina? jourdanensis, Paracoskinolina cf. hispanica, Urgonina alpillensis, Valserina sp. The microfossil assemblage includes other foraminifers such as Charentia cuvillieri, Mayncina bulgarica, Nautiloculina cretacea, Pfenderina globosa, Pseudocyclammina cf. lituus, Pseudolituonella gavonensis, Ammobaculites sp., Bolivinopsis sp., abundant trocholinids, various miliolids, other foraminifers and sparse algae which will be presented separately.  相似文献   

18.
Detailed stable carbon-isotope and biostratigraphic data based on ammonites allow us to reinterpret the timing of the different units of the Madotz section (62 m thick) in Navarra, northern Spain, relative to OAE-1a. We also infer bulk sedimentary rates and the duration of the intervals that include facies indicative of oxygen depletion. The lowermost part of the sequence includes the predominately clastic unit 1 (3 m) overlain in ascending order by subunits 2a (20 m), 2b (24.4 m) and 2c (basal 15 m studied) of the “Madotz Limestone”. Subunits 2a and 2c consist of Urgonian-type pure carbonate rocks. In contrast, subunit 2b consists of mixed carbonate–clastic facies (24.4 m thick) including beds of claystone and clay/shale with dispersed pyrite and scarce or no benthic foraminifera suggestive of oxygen-depleted conditions, and intermittent orbitolinid-rich intervals. δ13Corg data within subunit 2b, between 26.6 and 49.2 m show two excursions of 4.21 and 3.34‰, separated by a central segment with more uniform values around 22.56%. Compared to the high-resolution δ13C stratigraphy of the Early Aptian of the Alpine Tethys, these two positive excursions correlate with segments C4 and C6 of OAE-1a, whereas the central segment correlates with segment C5. New ammonite findings include Deshayesites cf. forbesi Casey and Pseudohaploceras? sp. in the uppermost part of unit 1, and D. cf. forbesi Casey, Pseudosaynella bicurvata (Michelin) and P. raresulcata (d'Orbigny) in the middle part of subunit 2b. The presence of D. cf. forbesi in unit 1 (0–37.7 m) and subunit 2b (lower 14.7 m), the first appearance datum of Pseudosaynella in subunit 2b, and the high relative abundance of Pseudosaynella specimens, support a stratigraphic position correlative with at least the upper part of the D. forbesi Zone (formerly D. weissi Zone). Such an ammonite faunal assemblage implies a lower stratigraphic position in the Lower Aptian (Bedoulian) than previously assigned to the section. Segments C4 and most of C5 comprise the lower part of subunit 2b and correspond to the upper part of the D. forbesi Zone. Based on chemostratigraphic correlations with published Spanish sections (Barranco de las Calzadas, Cap de Vinyet and Cau) in which calibrations of δ13Ccarb stages with ammonite zones was possible, we infer that the interval of the Madotz section between 37.7 and 53.1 m, or the upper part of subunit 2b and the basal part of subunit 2c, whose δ13Corg signal is indicative of stages C5, C6, and perhaps the beginning of stage C7, also correlates with the D. forbesi Zone. Average bulk sedimentation rate for C-isotope stages C4–C6 of OAE-1a ranges from 1.8 to 2.09 cm/kyr in the Madotz section. Facies indicative of oxygen deficiency are restricted to C-isotope stage C4 and part of C5 of OAE-1a. Hypoxic conditions lasted about 95.23–120 kyr and are coeval with deposition of the most prominent claystone and shale layers (1.8 m thick), which display the lowest TIC values (8.16–18.93 weight% CaCO3) and the highest TOC in the section (0.4–0.97%).  相似文献   

19.
Land-derived pollen and spores and marine dinoflagellate cysts were extracted from the Jurassic and Cretaceous sediments of the West Tiba-1 borehole, northern Western Desert, Egypt, On the basis of the recovered palynomorphs, of known stratigraphical significance, the following stages were assessed: Bathonian-Oxfordian (Middle-Late Jurassic) and Hauterivian, Aptian-Early Albian, Late Albian-Early Cenomanian, Early Cenomanian and Late Cenomanian (Early-Middle Cretaceous). No palynomorphs diagnostic for the Berriasian, Valanginian and Barremian stages (Early Cretaceous) were depicted. Based on the nature and composition of the identified palynomorph content, five informal palynomorph assemblage zones were recognised. These are: the Gonyaulacysta jurassica-Korystocysta kettonensis Assemblage Zone (PI, Bathonian-Oxfordian), Ephedripites-Aequitriradites verrucosus Assemblage Zone (PII, Hauterivian), Afropollis jardinus-Duplexisporites generalis-Tricolpites Assemblage Zone (PIIl, Aptian-Early Albian), Nyssapollenites-Elaterosporites Assemblage Zone (PIV, Late Albian-Early Cenomanian) and Assemblage Zone PV (Early-Late Cenomanian). The latter zone was differentiated into two subzones, namely the Classopollis brasiliensis-Elaterosporites klaszii Assemblage Subzone (PVa, Early Cenomanian) and Afropollis kahramanensis-Triporates Assemblage Subzone (PVb, Late Cenomanian). The time stratigraphy of the studied interval was revised. The occurrences and types of the dinoflagellate cysts, extracted from the studied succession, reflect a general shallow (shelf) marine pal˦oenvironment.  相似文献   

20.
An ammonite fauna from the upper Abderaz Formation of Kuh-e-Bul in the northwestern part of the Koppeh Dagh (Iran) is described and illustrated. The collection of 30 specimens is assigned to seven species, all of which are recorded from Iran for the first time: Pseudophyllites indra (Forbes, 1846), Pachydiscus (Pach.) haldemsis (Schlüter, 1867), Patagiosites stobaei (Nilsson, 1827), Menuites wittekindi (Schlüter, 1876), Glyptoxoceras retrorsum (Schlüter, 1872), Lewyites elegans (Moberg, 1885) and Trachyscaphites spiniger (Schlüter, 1872). This fauna is of a typical Boreal character, with all taxa having been described from northwest Europe originally. The stratigraphic range indicated by the ammonites is lower upper Campanian, below the first occurrence of Nostoceras (Bostrychoceras) polyplocum (Roemer, 1841) and probably above the last occurrence of Hoplitoplacenticeras (H.) vari (Schlüter, 1872). A nannofossil sample from the ammonite-bearing interval corresponds to the upper Campanian nannofossil zone UC15/CC22. Thus, on the basis of both ammonites and calcareous nannofossils, the upper Abderaz Formation is shown to be younger than assumed previously.  相似文献   

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